Ultrafiltration of mandarine juice by hollow fibre membranes

Modified poly(ether ether ketone) (PEEKWC) and polysulphone (PS) hollow fibre membranes were prepared via the dry-wet spinning technique through the phase inversion process and were tested for the clarification of the Clementine mandarin juice. Experiments were performed in selected operating conditions according to the batch concentration procedure up to a final volume reduction factor (VRF) of 2. The performance of the membranes was evaluated in terms of permeate flux and quality of the permeate. The permeate flux profile observed with the PS membranes was lower than that observed with the PEEKWC membranes. Almost all the total soluble solids and citric acid present in the feed were recovered in the permeate. The resulting juice after filtration showed a complete removal of suspended solids with a consequent improvement of color and clarity. PEEKWC membranes showed a lower rejection towards total phenolics (8.2%) in comparison with the PS membranes (16.4%). A high rejection towards total flavonoids was observed for both membranes (64% for the PS membranes and 55% for PEEKWC membranes); this phenomenon can be attributed to the strong association of these compounds to the colloidal fraction of the juice which is completely rejected by the membranes. Since phenolic compounds and total flavonoids contribute to the TAA of the juice, a consequent reduction of this activity in the clarified juice was observed. However, PEEKWC membranes showed a lower rejection towards antioxidant compounds (21.8%) in comparison with the PS membranes (32.0%).